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Arun

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HCl + Anhydrous ZnCl2 is known as Lucas Reagent. It is used to determine the DEGREE of an alcohol.The alcohol is reacted with Lucas reagent, and give alkyl halide along with water. The reaction follows SN1 mechanism, and a carbocation intermediate is formed, the stability of which determines the rate of the reaction. The alkyl halide formed is insoluble, and its formation causes the solution to become turbid, ie. cloudy.Now, Tertiary alcohols (which give 3 degree carbocations) and alcohols which give very stable carbocations on losing water after protonation (eg. resonance stabilised carbocations) react fastest and give immediate turbidity. Eg: t-butyl alcoholSecondary alcohols react a bit slower as their carbocations (2 degree) are not as stable as above mentioned ones. They give turbidity after about 5-10 minutes. Eg.: isopropyl alcoholPrimary alcohols react very slowly (1 degree carbocations are very unstable), and their turbidity comes after more than 45 minutes, and this is why they are said to produce no turbidity in the reaction mixture. Eg: EthanolThis way, degree of an alcohol can be found in most of the cases.